It's scientifically accurate in that "it's possible to grow plants on Mars, just not in the way done in the movie and certainly not in the way done in the book".

As for the way done in the movie:

But those nitpicking details could be crucial in real life.

The biggest problem, he said, is that Mars is about 1.5 times farther from the sun than the Earth is, and only gets about 60 percent of the light. This means that plants on Mars would grow at about 60 percent of the rate of Earth plants, even when exposed to full Mars light. Watney's habitat was designed to block radiation, which would lower the light levels even more.

"How would he get enough light for his plants? He didn't go into that. But plants need bright, bright light," Bugbee said. "We normally use a lot of solar panels and a lot of electric lights, but one of the things we're working on now is fiber optics: big, concentrating mirrors and fiber optics to bring that bright light in to grow plants."

Not to mention that the room, as shown in the movie, can easily be calculated to be significantly too small even if it was getting Earth light. But at least the situation in the movie (one order of magnitude too little energy to sustain a person) is better than in the book where potatoes are being grown on normal room lights;) Most people don't realize how much vastly dimmer it is, from an energy perspective, inside than outside - our eyes compensate for it, otherwise you wouldn't be able to see details in bright areas and dim areas at once. But that little "nitpicking detail" - 2-4 orders of magnitude too little light, give or take - is indeed critical to plants growing, and especially to them producing energy to store that humans can eat.

Had Weir had any experience whatsoever with growing caloric plants indoors, he would have realized this and there are many things he could have done in his design to ensure that the plants would get enough sun. The best option is exactly what the actual botanist above mentions: solar concentrators. A solar thermal power plant is a perfectly plausible way to generate electricity on Mars and Watney - had he been given a solar thermal farm and habitat with lots of transparent plastic - could have redirected heliostats to reflect large amounts of light into the habitat and stripped off insulation (adding it back on every night) to compensate for the dramatically increased heat load. That would have thus avoided the solar to electricity losses and the electricity to light losses, giving an order of magnitude more power, as well as avoiding the need to have quantities of lights onboard hundreds of times brighter (and correspondingly more power-hungry) than you actually would ever find. And it's plausible he could have taken existing heliostats and aluminum scrap and significantly boosted their parabolic area and thus light output (assuming the drive mechanism could take the additional load or he could modify it to).

But, that's not how it went.

There's tons of other things that would have killed the plants grown as described in the book (getting caloric crops to grow right in sealed spaces indoors is difficult even in controlled circumstances, there's such a huge range of things that can suddenly and dramatically wipe them out - which is why, as mentioned in TFA, NASA has a whole department researching the topic to try to create the controlled conditions to prevent this), but let's just stick to the most fundamental aspects here for now. The light was, pardon the pun, the most glaring problem.;)

Unlike a lot of other "science fiction" books/stories, Andy Weir seemed to make a genuine effort to get as much right as possible, and did his best to drag along the film producer. If all of science fiction was at this level, it would be a miracle. And as you've pointed out, where the science does fail, it fails in such a way as to spark discussion and interest in the real science. I don't feel like my intelligence was insulted after having watched/read it, or that errors and omissions were a result of laziness or "the audience is too dumb/doesn't care anyway, so why bother". (Although the book was better than the movie in that regard.) If anything it served as a launching (punnnns) point for learning more about growing food on Mars and other similar problems.

Unlike a lot of other "science fiction" books/stories, Andy Weir seemed to make a genuine effort to get as much right as possible, and did his best to drag along the film producer. If all of science fiction was at this level, it would be a miracle. And as you've pointed out, where the science does fail, it fails in such a way as to spark discussion and interest in the real science. I don't feel like my intelligence was insulted after having watched/read it, or that errors and omissions were a result of laziness or "the audience is too dumb/doesn't care anyway, so why bother". (Although the book was better than the movie in that regard.) If anything it served as a launching (punnnns) point for learning more about growing food on Mars and other similar problems.

I think that's the main thing. Typically movie science is built around the plot with occasional nods or Easter eggs for knowledgeable people from the audience (ie using an actual ssh exploit in the Matrix). But fundamentally scriptwriters and directors get too caught up with the story to realize how much those inconsistencies drag people out of the story.

I hope they start realizing how much audiences value scientific sincerity and internal consistency.

A long time ago, we had what I'm going to call, "hard science fiction." In the back of these fictional works were a bunch of appendices which included, frequently, the actual maths involved in their story telling. These were dropped when the genre became more popular, sometime in the 1960s as I recall - fantasy was being included with the genre as well. If you go to an old, used, bookstore then you may be able to find such works - Clarke had some, as I recall.

Oh cool, I'll look into that, didn't realize that was once a thing. I've definitely noticed "technology" being used as a fantastical deux ex machina/superpower lately. I have mixed feelings about that, haha.

I'd argue that the film still qualifies as the first mainstream Science Fiction movie. They made a real effort to get the details right, to the point where (at least for the film version), it's reasonable suspension of disbelief, rather then the usual "fantasy movie with spaceships and explosions".

I like your idea about the heliostats, and that could have added more challenges, as he's now taking a big hit to his available electric power. It will be interesting to see what NASA comes up with to do this on purpose. I've been in a house that uses "light pipes" to collectors on the roof for daytime lighting, and that works quite well. Concentrating light from a suitable large collection area into the room sure seems like it would work. Of course you have to be careful to keep it stable in a windstorm, so a bunch of lightweight panels sticking up from the roof of a lightweight structure is asking for trouble, but with fiber optics you'd have more options.

The wind on Mars would not really be a big deal. The atmosphere is too thin to push things (heavier than microscopic dust particles) around. That is something the movie also didn't get right. The highest recorded wind speeds on Mars would feel like a very gentle breeze to a person (i.e. you wouldn't feel it at all in a spacesuit).

Sure, but you wouldn't want to do e.g. huge "sails" of mylar sheet, which would otherwise be a simple way to get very large very lightweight reflectors. Wouldn't take much for them to get carried away.

Well not exactly. In the book explains that the HAB had excellent CO2->O2 converters. Mars Atmosphere is 95% CO2. It just requires energy, which comes from solar panels. So he had near infinite O2.-spoilers-The chemical conversion he does involved turning O2 and Hydrogen into H2O, which basically just involves burning Hydrogen. But burning hydrogen is very dangerous, so he puts on his spacesuit and empties the room of all the O2 (which requires a good bit of tricking the computer system). And slowing feeding the system just enough O2 and H to burn into water.Unfortunately he forgot that his spacesuit slowly leaks out O2 when he breaths out. So the room slowly filled with O2 until it reached a critical point and the entire room exploded. Much bigger explosion than in the movie apparently.

Ah that's right (I did read the book, just didn't recall the specifics in detail). I feel like even if all that is only 90% or so plausible, I still learned something about applied chemistry. As opposed to "you can survive for a few moments wearing street clothes in a vacuum if you hold your breath" as seen in other stories/movies.:|

Besides, even the author of the book admits that the sandstorm that got Watney stranded on Mars in the first place would have been impossible in real life. Martian sandstorms just don't have enough force to knock over a mars return rocket like that.

Actually, if they told him to use the MAV, that gives him permission, right there. I think that they left the pirate thing in because it was funny, not because it was right. There are times that that's the best choice and this may have been one of them.

I'd heard that, in it's day, Barney Miller was considered one of the more accurate cop shows. Lots of time spent filling in forms, writing reports. Occasionally, taking a statement, and maybe once or twice a year, a foot chase.

A few years ago I saw a comedian on TV who was talking about watching Dr. Doolittle with his wife who happened to be a lawyer. When Dr. Doolittle's wife offered to defend him in a court case, the lawyer wife said "That would never happen in real life, the court would never let a spouse represent a defendant". The comedian responded with "Did you miss the part 5 minutes ago where they had a talking alligator?"

A few years ago I saw a comedian on TV who was talking about watching Dr. Doolittle with his wife who happened to be a lawyer. When Dr. Doolittle's wife offered to defend him in a court case, the lawyer wife said "That would never happen in real life, the court would never let a spouse represent a defendant". The comedian responded with "Did you miss the part 5 minutes ago where they had a talking alligator?"

That makes for a good comedy sketch, but it's not a good counterargument to the wife's complaint.

Many stories include selected unlikely/impossible elements about which we intentionally suspend disbelief, but which we expect to be realistic in every other respect. We also accept other changes to reality that logically follow from the one we're choosing to accept, but there's no reason why the existence of a man who can talk to animals would be expected to affect a court's decision about conflicts of intere

My dad has some Norwegian ancestry, and one day when my parents were visiting we were all watching "How to Train your Dragon" with the kids. My dad, being a bit of a know-it-all, kept bringing up that Vikings didn't really dress/act like that.
Somehow he missed the part about it being a kids' cartoon where the Vikings fight dragons on a daily basis. It's not real life, dad!

I hear programmers complain all the time when programming is represented horribly in movies. Honestly, I think he was incredibly nice about the book's terrible portrayal of botany. The book's description of the growing of caloric crops indoors is the botanical equivalent of someone writing a programmer into a book like:

Haxx0r wandered around the code, scanning the macros with his VR headset. A greenish slime dripped off of the prime for-loop. "Now where did that come from... " he pondered. Suddenly a loud

You sound just like your typical computer illiterate person getting mad when listening to a programmer complain that the programming in a TV show is nonsense. "What is it with you, why do you have to comment about how your job is represented in movies or TV series?"

Yes, I've heard both from lawyers and from people who do cattle work complain about depictions in movies. It would be one thing if it was just about watching the movies, which I know plenty of people can suspend disbelief for even stuff related to their job, or at worst laugh about it. But way too many people form opinions or ideas from what they see in movies, even for some bright and intelligent people who just haven't been exposed to any other source of information on a particular topic. I've had to d

The nutrient levels in martian soil are lower than on earth, but they are not zero. With some work, which Damon's character does in the film, it is not inconceivable for someone with sufficient botanical skill to accomplish what he does... (although I do suspect it would take more effort than what the film depicted).

Martian regolith contains perchlorates. It's toxic. We're not talking about nutrient levels. It's up to 2% by mass perchlorate ion. Perchlorates are rocket fuel. Literally, they've actually considered harvesting them to make propellant on Mars [aiaa.org]. They're also quite toxic, impeding thyroid function at a couple dozen parts per million quantity in water. They're toxic to plants too.

You can't just, like in the book, take some martian regolith, take some manure, sprinkle on some dirt for bacteria (which was BTW a pointless step given the crop choice and the bacteria already present in the manure), mix it all together and call it a growth medium. First you have to bake the regolith to break down the perchlorates. Then you have to rinse it to remove the extra salts. Then if you have a reverse osmosis system you could add the water back in. There's still no guarantees then that it'd be fertile/have all of the needed nutrients in approximately the right ratios, but at least it's not guaranteed to be a health hazard to both you and your plants.

He's going to fertilize the potatoes with vitamins? Plants, including potatoes, need NPK (nitrogen, potassium and phosphorous) as well as various micro-nutrients, all in a form that can be taken up by the plants.Whether human manure and piss would supply enough when starting with regolith I don't really know but doubt based on my gardening experience.

Perchlorates may lead to health problems but likely not deadly. According to some groups, perchlorate affects only the thyroid gland [wikipedia.org]. Because it is neither stored nor metabolized, any effects of perchlorate on the thyroid gland are fully reversible. Some other studies suggest that perchlorate may have pulmonary toxic effects as well. In this article [space.com]it is mentioned that exposure could be managed. As for using the soil for agriculture, there are several technologies can remove perchlorate, via treatments ex situ and in situ. Ex situ treatments include ion exchange using perchlorate-selective or nitrite-specific resins, bioremediation using packed-bed or fluidized-bed bioreactors, and membrane technologies via electrodialysis and reverse osmosis. In ex situ treatment via ion exchange, contaminants are attracted and adhere to the ion exchange resin because such resins and ions of contaminants have opposite charge. It may be beneficial to process it. Researchers have proposed [space.com] a biochemical approach for the removal of perchlorate from Martian soil that would not only be energetically cheap and environmentally friendly, but could also be used to obtain oxygen both for human consumption and to fuel surface operations. In any event, precautions will have to be taken but the presence of perchlorates in the soil does not appear to be 'show stopper' at this point.

First you have to bake the regolith to break down the perchlorates. Then you have to rinse it to remove the extra salts. Then if you have a reverse osmosis system you could add the water back in....

From what I read [researchgate.net] the perchlorate content is 0.5-1.0%, which is still a lot, but there is no need to "high-ball" the estimate. Watney would have known about this quite well, and could very well chosen soil at the low end of the range.

Also the perchlorate removal process could be a lot simpler than you assert. As the article above points out: "Perchlorate salts are very soluble in water...". Simply leaching the soil through his evaporative recovery cycle could remove perchlorates just fine (although the lengt

You routinely mix *real* science and *fiction* in this type of writing.

Every Si-Fi Movie I've seen in my lifetime had assumptions or plot devices which where hopelessly impossible based on known physics. The trick is to make the story engaging enough so that the majority of people reading/watching will suspend their thinking about reality and science and just enjoy the story. My favorite example was "Gravity" where orbital dynamics where simply ignored wholesale, mainly because what would take weeks/months/years to develop in reality, needed to happen on much shorter time frames for the sake of the story. If you liked the movie, I'll bet you didn't notice this the first time you watched it. You suspended scientific reality, and it doesn't really matter. It was a movie...

So, who cares if the scientific reality doesn't quite match the story? Of course it's always interesting when the author is clever enough to keep the impossible technology to a minimum, but let's face it. If it took hours to shuttle down/up from a ship in orbit, decades to get to the next solar system and decades to get a message to/from headquarters the stories would be really slow paced.

>My favorite example was "Gravity" where orbital dynamics where simply ignored wholesale, mainly because what would take weeks/months/years to develop in reality, needed to happen on much shorter time frames for the sake of the story. If you liked the movie, I'll bet you didn't notice this the first time you watched it.

I gotta tell you, my grasp of orbital mechanics is at Kerbal levels, but that was enough that it ruined major portions of Gravity for me.

It would have been better if the movie (like Interstellar) hadn't been promoted as scientifically accurate when there was obviously no real intention to make it so.

Kip Thorne (the scientific adviser who let his name be used for this) wrote a book called "The Science of Interstellar". The original plan had been to make a scientifically accurate movie, but as happens in Hollywood other people came in with other ideas. Thorne wound up saying that there was nothing in the movie he knew to be definitely impossible, although it got really improbable.

I'm not a good enough physicist to know for sure, but it looks to me like a black hole acting as a wormhole should have g

The difference is that Andy Weir actually did try to make it as scientifically accurate as he could (besides the windstorm scene). He got a lot of stuff right. IIRC, he's actually worked for NASA, so he knows quite a bit (and knows people who know more) about space exploration. (It was either Andy Weir or Randall Munroe who said that no matter what you do at NASA, if you work there you tend to talk a lot about space.)

A lot of people look at the book (haven't seen the movie) as being the closest to a scie

No, he never worked at NASA, he just read the publicly available information. He computed all the trajectories to make the date match up so he had a reason for the potatoes being on the mission though.

okay, you've convinced me to not watch the Martian. If the defense of a movie that is supposed to be scientifically accurate, and isn't, has to resort to comparisons involving Plan 9 then it just isn't worth watching.

besides, I don't see the guy making specific predictions about what would happen. What someone should do is use the data we have on martial soil to duplicate the setup and see what happens.

Also, I think that the martian light issue isn't a deal. Even in the book, the station would have to be opaque so it is purely a question of whether he had sufficient artificial lighting inside the station. I don't recall if that was a addressed in the book or not but it would have been overly bright and hard to watch so wouldn't be emphasized in the movie.

MST3K-level BS on every page, but still, let's keep calling it "hard" science fiction because the author constantly spouted calculations - even though almost every last one was done wrong and spoke to a significant lack of understand of even the basics of the topics he was writing about.

To their credit, the movie's approach was vastly more realistic than the approach in the book, using natural light rather than room light, and adding a grow tent so that the moisture doesn't condense in every last nook in the electronics systems and kill him, rather than peacefully "raining down" as in the book (it's amazing how much moisture growing even just a few square meters of plants pumps into a room... I remember being confused why the breaker to my bathroom would immediately throw whenever I flippe

Freeze dried (to reclaim 99+% of the moisture), vacuum sealed, and then dropped in a box in the open mars "air"... There would be almost ZERO pathogens left in it. So, it's a source of nutrients but nothing else. The problem is nitrogen. It's completely unlikely NASA sent any nitrogen fixing bacteria with them, so the ammonia (urea) from human waste (and his hydrogen generator) would be useless -- actually toxic.

The movie took lots of liberties and simplified (or eliminated) the detailed explanations in the book. In the book Watney explained that he had live soil that he used to "seed" the compost/dirt mixture.

Biosphere II's numerous points of failure [kenyon.edu] proved that part. Materials used in construction, unanticipated environmental considerations like simple condensation problems or oxidation, and ecological relationships between competing organisms proved too much for the engineers and scientists to anticipate.

Sustainability is a popular subject taught in western public schools and based on similar assumptions to those of other Cartesian reductionist approaches to 'the sciences'. But as the climate skeptics argue,

'nuf said.By the way, how much perchlorate was in the regolith simulant?The problem with simulations is that they are just that---simulations.

The perchlorate question is interesting, but really depends on the environment around where it was found. The water in the movie was created from hydrazine, so (presumably) it was not an area with large amounts of water ice already, and thus lower concentration. That said, use oif the rocket fuel in this case could have resulted in a perchlorate sparing reaction to take it out of the soil; I assume if that was intended, it ended up on the cutting room floor, but it's technically doable.

“It's mostly iron oxides. And iron makes stuff red, like rust. So it would be pretty hard to just take soil the way he did in the movie and put a little bit of composted human waste on the plants, and magically grow these great potatoes."

I'm not a botanist, so maybe I need the remedial version, but what does iron making stuff red have to do with any of this? Are there other qualities of Martian soil that would make it bad for growing things besides the red color?

As far as I know there is red, iron-rich soil many places on Earth as well.
According to a book I read about Hawaii, an industrious land owner treated car wrecks with sulfuric acid to supply the soil with more iron in order to grow more pineapples.

I think this guy was talking through his hat. Average Martian soil is about 18% iron oxides [usra.edu] which makes it lower in iron content than many Hawaiian volcanic soils [google.com], in fact the composition of Martian and minimally weathered Hawaiian soils are often compared. And we know what a barren wasteland devoid of life the Hawaiian islands are...

I just want to say, most people have no idea how many plants one must grow in order to survive. If you, 1 adult, want to get most of your calories from a plant, a potato is a decent choice. You can plant 5 kilos of potatoes in a 30 meter row, and expect ~ 90,000 kC. Since they take 90-120 days to mature, in order to have a continuous supply, you'd want maybe twice this many, along with lots of other plants that supply calories, protein, vitamins, and flavor. Two rows of potatoes are about a meter wide, so y

The movie took lots of liberties and simplified (or eliminated) many of the detailed explanations in the book. Don't look at the movie for scientific accuracy; it isn't. The movie is a product of Hollywood after all.